Yes, the rock-scissors-paper analogy that zhuge mentions is key. The thing I always do when starting any game is do enough 2v2 unit battles to know what units beat what units, how to use terrain (hills and tree cover), and the other things that zhuge mentioned.

Having only two units to control also helps you learn the basics of strategy, which is how you will win battles. For example, if you have foot soldiers, archers, and cavalry in an army, then every time, put your archers in a line slightly ahead of your foot soldiers (who also need to be in a line, or maybe two if you have lots), and put your cavalry out to either side.

That position alone will help you win 50% of your battles. Using that setup and then moving your cavalry around the enemy's flank, on the other, will help you win 90% of your battles against the computer AI.